Based on toxicology studies, benzimidazoles such as Fenbendazole, Mebendazole or Albendazole seem to be safe drugs.

However, a drug without any side-effects does not exist. Scientific data reports do not reveal significant adverse reactions from taking fenbendazole. Despite the fact, there are anecdotal reports of potential toxicity:

• Up to 5 % of people can experience stomach discomfort or diarrhea when taking large quantities of fenbendazole with no breaks.
• People with severe liver or kidney failure have lower medication excretion rates, therefore, fenbendazole can accumulate and cause unexpected side-effects. Doses should be divided accordingly in this situation.
• When used in large quantities for a long period of time without breaks, fenbendazole can cause an asymptomatic liver enzyme increase due to the fact of the substance being mainly metabolized in the liver. This is reversible with the help of a couple week pause from the medication.

The protocol was designed to keep the liver in optimal health, therefore the schedule of weekly 3 days on, 4 days off was previously suggested. However, more and more people are using fenbendazole on a daily basis without problems.

We would still recommend taking at least 1 day off per week to avoid overstressing the liver if the medication is to be used for prolonged periods of time (like months or years).

To keep the liver health optimal, we advise you to take 250 mg capsules of Milk Thistle or 150 mg of Silymarin daily as a supportive supplement for keeping it in great shape.